The invention relates to an apparatus for transcutaneous application of a stimulus or for transcutaneous measurement of a parameter on or from the skin surface of a vertebrate, in particular a human.
Apparatuses of this type are in use in particular for therapeutic electrical stimulation of the vagus nerve (nervus vagus) in order to achieve a medical effect. Concerning this, it is known with apparatuses for transcutaneous stimulation of nerves or acupuncture points to exert an influence on the neuroelectrical or other characteristic and thus on the function of the nerves to be stimulated or on the tissue by invasive or non-invasive electrical stimulation of the nerves or of the surrounding tissue using clip systems (similar to a clothes peg) or pin-like systems or with the assistance of small needles which, after connection to a control unit, are additionally stimulated electrically. The aim of such a procedure is usually to elicit somatization alterations such as, for example, stress diminution.
Of particular scientific importance are on the one hand stimulation of nerves and tissues in the region of the ear, especially electrical stimulation of the portions of the vagus nerve located there, or stimulation of tissues and nerves by means of caloric, magnetic or other types of stimulation, and the detection of various physiological, pathophysiological or physical parameters such as, for example, body temperature or oxygen saturation.
The non-invasive stimulation of the vagus nerve, the principal nerve of the parasympathetic nervous system, which leads to skin afference in the region of the external ear, is at present mentioned in a few instances in the scientific literature for diagnostic and therapeutic purposes for neurodegenerative disorders such as Alzheimer's, Parkinsonism or epilepsy, reference being made to Ventureyra ECG: “Transcutaneous vagus nerve stimulation for partial onset seizure therapy”, Child's Nerv Syst (2002) 16: 101-102, and to Fallgatter A J, Ehlis A C, Ringel T, Herrmann M: “Age effect on far field potentials from the brain stem after transcutaneous vagus nerve stimulation”, Int J Psychophysiol (2005) 56: 37-43, and Fallgatter A J, Neuhauser B, Herrmann M J, Ehlis A C, Wagener A, Scheuerpflug P, Reiners K, Riederer P: “Far field potentials from the brain stem after transcutaneous vagus nerve stimulation”, J Neural Transm (2003) 110: 1437-1443. In the study by Ventureyra it is merely suggested that it is possible to apply electrical stimuli to the ear in order thus to treat epileptic seizures. No approaches to a solution for an application apparatuses are indicated. In the studies by Fallgatter et al., a stimulation electrode and a reference electrode are placed on a piece of copper plate which is coated with epoxy resin and attached to the ear with a sticking plaster in order thus likewise to employ electrical stimuli for diagnostic purposes after recording an electroencephalographic signal (measurement of currents in the brain) with a commercially available instrument. Such a self-made apparatus is not suitable for accurate placing of the electrodes on the external ear because it must be attached with adhesive tape and does not simulate the shape of the external ear.
For accurate placing of a sensor or a sensor unit for measuring physiological, pathophysiological or physical parameters or for electrical or other types of stimulation of nerves and tissues on the external ear or in the auditory canal, the following two apparatuses are known:
U.S. Pat. No. 5,458,625 describes an apparatus and a method for stimulating nerve portions, located a short distance under the skin of the external ear, of the vagus nerve for treating stress, pain or for muscle relaxation. The instrument comprises a pair of transcutaneous (acting through the skin) stimulation electrodes. These are designed in the form of clothes peg-like clips and are suitable for attachment to the ear lobe. A stimulating current which appears suitable for nerve stimulation is applied via the clip electrodes.
US 2003/195588 A1 proposes a multimodal nerve stimulator. An apparatus which may comprise various sensors and annular electrodes must be introduced deep into the external auditory canal to the site of action. It is further described herein that portions of the vestibularis nerve which might have positive properties in the treatment in particular of epilepsy and dizziness are stimulated in the external auditory canal. The apparatus additionally provides a constructional shape adapted to the anatomy of the auditory canal.
The following circumstances have proved to be disadvantageous with the previously disclosed solutions mentioned:
The scientific literature mentions—as indicated above—stimulation of the tragus or a defined anatomical portion thereof. The described clothes peg-like clip systems do not make it possible to stimulate nerve portions in the region of the external ear which are relevant to the therapy in particular of depression, epilepsy, cardiac symptoms and further neuropathological disease states. An additional factor is that the relatively high voltages, of 80 volt and more, which are necessary with such clip systems to overcome the resistance of the skin represent a very high risk of injury on application in particular to the tragus or other structures of the external ear.
Described clip systems are not, because of their mechanical retaining properties, suitable for application during a movement of the body. There is the risk that the connections will be broken. This in turn entails a risk of injury to the wearer from the now dangling cable connections, and the risk of damage to the electronics in the stimulation unit, for example from a short-circuit.
The previously disclosed apparatus of a multimodal neurostimulator explicitly describes an earpiece which is suitable only for introduction into the external auditory canal. Even the fabrication of such an in-canal earpiece is associated with great difficulties. It is necessary for this, based on previously disclosed methods, to use an impression material for making an impression of the ear in particular for an individual method of construction in order to be able to simulate as true to detail as possible the anatomical course of the auditory canal. Making such an impression is associated with various risks, in particular of injury to the ear drum and various parts of the skin of the tissue which is very sensitive there. Making an impression is made more difficult in the presence of otological pathologies such as, for example, a ruptured ear drum, and can be undertaken only by a skilled person.
The tissue of the external auditory canal is very susceptible to cutaneous irritation, and on introduction of foreign bodies, for example in the case of a previously disclosed neurostimulator, inflammations and allergies may occur in particular as a long-term effect.
In the case of a non-individual design there is an increased risk of injury to the auditory canal structures through the fit being inaccurate.
According to the document mentioned, only the vestibular nerve is stimulated by the indicated earpiece present in the auditory canal. This nerve is a sub-branch of the vestibular cochlear nerve which has only purely sensory types of fibre. This makes it possible to exert an influence on the organ of balance of a vertebrate and thus on manifestations of dizziness, nausea or spatial orientation, but not to stimulate further nerves, especially the vagus nerve.
Attachment of sensors to such a piece fitting in the auditory canal and having cutaneous contact with the external auditory canal appears worthwhile. However, the following disadvantages should be mentioned: the cutaneous tissue of the external auditory canal continuously produces cerumen which also has the colloquial name earwax. This secretion is deposited on the surface of the sensors and thus falsifies the results of measurement. In addition, it leads to an extensive and persistent contamination of the sensors, which is likely to have effects on the useful life of such a system. In addition, a lack of connection to the external ear, where numerous parameters can, however, likewise be picked up in an advantageous manner, and to the environment as carrier of additional useful sensory information, is regarded negatively.
Finally, the design of the stimulation electrodes is regarded as disadvantageous. The described previously disclosed solution describes electrode loops placed annularly around the earpiece. However, these have a limited area and do not permit stimulation of a defined area in only one dimension or stimulation of portions of the external ear.
For large-area therapeutic and diagnostic use of the method of transcutaneous nerve stimulation on the ear, and measurement of various parameters, it is desirable to integrate a therapeutic and sensory system in a convenient, safe apparatus which can if possible be individually adapted and can be worn at any time without complication, comfortably and inconspicuously, and is suitable in particular for attachment to or in the external ear.